void LoadDS()
{
List <PhieuNhapDTO> dsPN = PhieuNhapBUS.GetDSPN();
dgvDSPN.DataSource = dsPN;
for (int i = 0; i < dgvDSPN.Rows.Count; i++)
{
dgvDSPN.Rows[i].Cells[0].Value = i + 1;
}
btnThem.Enabled = true;
btnSua.Enabled = true;
txtMaNhap.Enabled = true;
btnLuu.Enabled = false;
}